1. Field of the Invention
The present invention is related to a method of operating a bale opening machine having an opening member wherein the height of a row of bales is determined by means of at least one sensor directed towards the bale surface and is used to control the position of the opening member during the subsequent bale opening, and also to an apparatus for carrying out this method.
2. Description of Background and Other Information
A method and apparatus of the aforementioned type is described in DE PS 31 53 246. In the known apparatus, three sensors in the form of optical proximity switches are mounted on the arm which carries the opening member. This arm is manually moved over the first bales of the row of bales. After actuating a start button, the arm sinks downwardly. As soon as the first sensor transmits the signal, the instantaneous count is stored in a memory. The same takes place for each further sensor. When the last sensor has also transmitted its signal, the downward movement is stopped, the tower with the arm continues to move at a slow speed along the row of bales, and the arm is moved upwardly to the level at which the first sensor responded, plus a certain amount. Once it has reached this height, the arm again sinks downwardly and the height determination takes place again as described above.
In the described manner, a plurality of measured values is obtained from which an average value is formed which is used for the further working-off process. Because the arm of the opening member moves continuously upwardly and downwardly when carrying out the measurements, a relatively large amount of time is lost for the one time derivation of the height profile of the row of bales. Furthermore, the aforementioned document does not describe how the actual opening process is carried out, starting from the average value, with this opening process naturally taking place during a later movement of the arm along the row of bales. A predetermined in-feed amount, or advance, is presumably preset starting from the average value, i.e., the arm with the opening member is caused to sink beneath the average value by a predetermined amount and the opening takes place with this fixed preset in-feed. The object of this first opening pass is to bring the row of bales to a uniform level so that, in subsequent opening passes, one can always operate with fixed preset in-feed depths. This known method does not take account of the differing hardnesses of the different bales or of the different components of the row of bales.
The present Applicant's European Application No. 85 115 579 (Publication No. 193 647) describes a method of removing fiber flocks from textile fiber bales in which the in-feed for each opening movement along the row of bales is selected in accordance with the bale hardness in different regions of the bales. This embodiment takes account of the fact that the bales have a varying density, i.e., hardness, and indeed such that the hardness is lower in the upper and lower regions of the bales than it is in the middle regions, so that the in-feed depth in the upper and lower regions may be larger than in the middle region.
This document does not, however, describe the determination of the hardness of the bales. This is, however, of great importance in practice, at least if it is desired to operate a bale opening machine at the upper limits of performance, in order to economically obtain maximum production. Although one can operate with values for the hardness of the individual bales which are determined with experience, in many cases this is not very accurate. For example, when putting together a row of bales of different origins (called components) the material is frequently manually lifted from the higher bales of one component and placed on the lower bales of the same component. In this way the assumed hardness distribution of the individual bales is falsified. Furthermore, since bales of different origins originate by definition from different regions, they are thus pressed together using different plants and have different fiber characteristics, so that the hardness distribution in the bales of different origins is also different.